Gold triangular nanoplates with edge effect for reaction monitoring under dark-field microscopy

True morphology imaging of individual nanoprobes with high sensitivity and in situ dynamic response is crucial in the dark-field microscopy imaging analysis. However, the geometry and orientation of the probes are experimentally challenging to visualize as their physical dimensions are usually below the diffraction limit. In this work, two-dimensional triangular gold nanoplates (AuNPLs) with the edge length > 600 nm and the thickness ~25 nm displayed clear triangular-shaped far-field scattering patterns (TFSPs) under a dark-field imaging system owing to the strong electrical field strength around the sharp edges and tips. Thus, their actual shape and orientation specific scattering image are directly visualized only by dark-field microscopy and furtherly applied to real-time monitor the etching and alloying progress of AuNPLs. The results showed that the reactive sites of AuNPLs are located at their vertices and sharp edges owing to the sensitive edge effect. This work provides a new perspective to directly monitor the conformation and dynamics of chemical reaction at the single particle level.